(Attorney Michael Barrett, second from left, announces a lawsuit by the family of slain Philadelphia police officer Moses Walker against the Pa. Parole Board. Third from left is Walker's mother, Wayne Walker-Lispcomb. Credit: Paul Kurtz)

By Paul Kurtz

PHILADELPHIA (CBS) — The family of slain Philadelphia police officer Moses Walker Jr. has filed a federal lawsuit against the Pennsylvania Board of Probation and Parole.

The suit names the board chairman, two supervisors, and a parole officer.

Lead attorney Michael Barrett says Jones was released from prison ten days before Walker’s murder, and was supposed to be under house arrest and electronic monitoring. But the system was never set up.

In addition, the suit says, Jones should have been sent back to prison because he failed a drug test in violation of his probation, but two board supervisors declined to take action.

(Officer Moses Walker. Phila. PD photo)

Officer Walker (right) was shot to death August 18th while walking home after his shift (related story).

Walker’s mother and other relatives say his murder could have been averted had the Board of Probation and Parole done its job.

In their suit, they say that confessed gunman Rafael Jones should have been behind bars because he was in violation of his probation after testing positive for drug use (see related story).

“Officer Walker’s murder occurred as a result of a failure on the part of all the defendants to this lawsuit that we filed to have in place proper and effective policies and procedures to protect the citizenry at large and in particular, police officers,” Barrett said today.

In addition to the two supervisors, the suit names Jones’ parole officer and board chairman Michael Potteiger.